title: In vivo tissue response to ultrasound assisted application of biodegradable pins into cortical and cancellous bone structures: a histological and densitometric analysis in rabbits.
abstract: In orthopaedic traumatology biodegradable pins are increasingly used for fixation of small bone fragments. In the present study, the ultrasound-assisted anchoring technique (SonicFusion technique), a osteosynthesis method being recently introduced in cranial applications, in which ultrasonic  energy is used to insert and anchor polymer pins in bone, was compared with the conventional pin application procedure. The aim of the present study was to assess the short and long term thermal impact of two different ultrasonic energy levels on different bone structures in the distal medial  femur of rabbits. The treatment groups consisted of customized polylactide pins applied at a low and a high energy level, the Reference Control and a Negative Control. The thermal effect on bone tissues was evaluated by means of qualitative and semi-quantitative histology and micro-computerized  tomography. Five days following surgery, all implant sites showed no tissue damage but normal signs of early ongoing tissue repair. Enhancing the energy level by about 30% had no significant impact on the tissue response. At 4 weeks after surgery test sites covered by ultrasound-aided implantation  showed a significantly enhanced bone/implant contact as compared to pins applied by conventional application. In conclusion, the ultrasound assisted anchoring technique not only did not impair bone regeneration, but even improved implant integration.
authors.affiliation: Stryker Osteosynthesis, Dr. Homer Stryker Strasse 1, CH-2545 Selzach, Switzerland. joerg.arnoldi@stryker.com
authors.forename: Jörg
authors.initials: J
authors.lastname: Arnoldi
authors.forename: Philip
authors.initials: P
authors.lastname: Henry
authors.forename: Philip
authors.initials: P
authors.lastname: Procter
authors.forename: Bernd
authors.initials: B
authors.lastname: Robioneck
authors.forename: Anders
authors.initials: A
authors.lastname: Jönsson
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D015519:Bone Density; D001858:Bone Nails; D003720:Densitometry; D005260:Female; D005269:Femur / Q000166:cytology* / Q000000981:diagnostic imaging / Q000502:physiology*; D019637:Orthopedic Procedures / Q000009:adverse effects / Q000379:methods*; D011817:Rabbits; D013696:Temperature; D013997:Time Factors; D014465:Ultrasonics; D055114:X-Ray Microtomography